Both hard fouls were against Celtics rookie Grant Williams and led to Allen being tossed with 9:12 remaining in the fourth quarter.
Allen, the 21st overall pick in the 2018 NBA draft,, played last season with the Jazz as a rookie and was part of the trade that sent Mike Conley to Utah.
Allen also picked up a technical foul earlier in Thursday’s game, and in his summer league debut with Memphis on Sunday.
At various points during his four-year career at Duke, Allen was reprimanded for tripping opponents, a habit that led to a one-game suspension in 2017 and Allen being stripped of his Blue Devils captaincy.
Allen’s ejection was the third of this year’s summer league, following Spurs forward Drew Eubanks on Monday and Lakers forward Nick Perkins on Wednesday.